Frequency domain optical reflectometer.

A correlation reflectometer operating in the frequency domain is described. It is shown that such an instrument is well adapted to detecting weak discrete reflections. The detection of end reflections in a 2.2-km length of fiber whose end is index matched is demonstrated. A round-trip range of over 70 dB is obtained with a 1-mW optical source power. The method shows promise for characterizing the reflective properties of optical fiber elements, such as tapers, microbends, and splices, and may be useful in fault location.